Self driving C10

[68Blu]

Hey everyone, at my wits end with this truck. Won’t bore you with the saga but need serious help. A few days ago I noticed the engine revving high while cruising on the highway. Like I was flooring it from a dead stop high. Turned onto my street took my foot off the brake, did NOT touch the gas, and the suddenly she’s doing 30mph. I thought maybe pedal was stuck so stopped, hooked my right foot under the gas pedal and let off the brake. Nope, hit 25mph right now. Thoughts on what’s causing it? Thanks!

[truckster]

Can you give us more detail? Year, engine, trans, carb, etc.

[68Blu]

Sure. 68; Chevy SB 350/355 (less than 2,000 miles on it); Holley Sniper EFI; 700r4 trans; tank relocation to the rear; Doug’s headers; dual exhaust; power steering; Lokar pedals; Dakota Digital cluster; dual fan radiator.

[truckster]

I'm just grasping at straws here... does the Sniper require a return spring? Does the throttle return to idle if you move it by hand under the hood?

[KQQL IT]

Vaccum leak

[special-K]

I know nothing about the Sniper EFI. What type of linkage is used? Still the original rod type? If it stays revved when lifting the peddle either linkage on unit is not moving with pedal to unit linkage or it's an electronic issue I'd guess.

[LockDoc]

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I don't know anything about the electronic stuff either. If the linkage is still the rod type as Tim mentioned a broken motor mount (or 2) can cause that.

LockDoc

[68Gold/white]

Sounds sorta like “Snipe Hunting” in days of old.....Lol...

[BigBird05]

The broken motor mount issue was so bad in the 60's that GM had to come out with a engine limiting saftey strap to keep the engine from running away. It seams that the throttle rod would stick and the carb linkage would stick in the open position.

[hugger6933]

Sounds to me like a vacuum leak. Spray carb cleaner or contact cleaner around the intake ends along the heads where the intake is mated, end seal of the intake and under the throttle body unit along the gasket mating surfaces. as you spray listen for changes in you motors sound or RPM's. If it indeed does change RPM's you sir have a leak that needs to be addressed. Good luck. Jim

[da.slyboy]

Do you have the the small screen controller hooked up to your Sniper? What does the TPS sensor show with no gas depressed? Depending how you setup the throttle linkage it's preferred to add a return spring. I want to say something funny is happening with the Sniper how it sees the throttle. I don't believe it will add more gas with a vacuum leak while driving unless it sees/senses the throttle depressed. At idle it may open the idle control more only if the engine is trying to die.

[KW5413]

Originally Posted by 68Blu

Sure. 68; Chevy SB 350/355 (less than 2,000 miles on it); Holley Sniper EFI; 700r4 trans; tank relocation to the rear; Doug’s headers; dual exhaust; power steering; Lokar pedals; Dakota Digital cluster; dual fan radiator.

Sniper linkage is known to stick. I have it on my 1976 cutlass w/built 350 rocket The linkage was very stiff and would often stick, leaving me with high rpms to deal with. I would have to ''kick it down'' to get it down to idle. Sometimes I would have to pull over and spray the linkage with WD to get some safe driving in...for a while.

The stiff petal would cause the car to lurch when starting off or trying to move in short increments.

If you don't have one of theses...get, or fabricate, one.

https://www.efisystempro.com/sniper/...on-lever-20-16

Even though it looks to be out of stock I would contact them anyway.

Completely resolved my stiff throttle issue and greatly relived my sticking linkage issues, though I am still experimenting with spring strength and still lubing up all the moving parts. But, it is a LOT better.

For the short term, try keeping the linkage lubed up...see if it helps.

[68Blu]

Thanks everyone. Was finally able to pin it down to the linkage. All is good �� I will definitely be watching the lubrication and keeping up with it as well as investigating the link above. Happy thanksgiving ������